Washington DC – The world's richest man apparently isn't taking kindly to Democrats' new billionaire tax proposal.

Elon Musk, CEO of Tesla and SpaceX, has a net worth of over $240 billion. You'd think that'd be more than enough to go around – but Musk seems to disagree.

Musk lashed out on Twitter after Senate Finance Committee Chairman Ron Wyden proposed a yearly tax on billionaire's unrealized capital gains, or investments that have increased in value without being sold.

The entrepreneur responded to a tweet which included a letter for constituents to send to Congress members as a way to oppose the new tax.

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"I expect you to oppose the Wyden proposal to tax unrealized capital gains," the letter reads. "I anticipate that any new unrealized capital gains taxes will slowly make their way down to middle class retirement investments over the next several years. It will start with billionaires, then eventually millionaires, then the modest investments will get hit possibly within a decade."

Musk, who is on track to become the world's first trillionaire, expressed his approval in the comments: "Exactly. Eventually, they run out of other people’s money and then they come for you."

Wyden responded to Musk's remarks, saying, "The people who are clearly trying to be tricky are people who are trying to find a way to not pay taxes. In this case, the scandal is what is legal."

The tax plan is part of some Democrats' strategy to fund their reconciliation package, which would make a historic investment in Medicare, childcare, community college, affordable housing, climate action, and other social programs.

Wyden announced his Billionaires Income Tax proposal on Wednesday, with his office saying they expected the measures to raise billions of dollars in revenue, according to The Hill.

Only about 700 individuals are expected to be affected by the proposal, which is designed to get around issues of tax avoidance.

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With Arizona Senator Kyrsten Sinema opposed to funding reconciliation through higher tax rates for corporations and high-income earners, Wyden's proposal may be a way to bring her on board.